It is known to provide a gas lift pump for pumping a fluid such as a liquid or sludge. JP2007113295 discloses an air lift pump for excavating sediment and sludge that has deposited and hardened on a sub-aqueous bottom over a period of time. The pump has a riser pipe whose lower end header reaches as far as the sub-aqueous bottom; a nozzle which is enclosed by the header and sprays high-pressure fluid, and a blade for scraping material from the sub-aqueous bottom.
JP1207535 discloses an air lift pump for pumping mud from a water bottom such as a river bed.
In an entirely separate technical field, the problem exists that aquatic nuisance species (ANS) such as Zebra mussels are being transported between locations such as between the US and Asia in the ballast tanks of maritime vessels. Aquatic nuisance species may be defined as waterborne, non-native organisms that threaten the diversity or abundance of native species, the ecological stability of impacted waters or commercial, agricultural, aquacultural or recreational activities. A variety of measures for preventing invasion of an environment by ANS have been proposed, including purging of ballast tanks at sea before a vessel enters an area sensitive to ANS.
However, purging of a ballast tank requires emptying and refilling of the ballast tank. It will be understood that such a procedure can have an adverse effect on the stability of a vessel particularly in rough seas and is not appropriate in certain cases.
It is also known to kill ANS by pumping inert gas into seawater. The inert gas can for example be supplied by or derived from the combustion gases of a marine engine such as a diesel engine.